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Math Help - Basic Graphing help

  1. #1
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    Basic Graphing help

    Hey all, fisrt of all i'm not sure if this should go here or not but I didn't know where to post it... I'm having a bit of trouble with math and hoping someone can explain it to me.

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    Water is being poured into a container as illustrated below at a constant rate. The height of the water level is then recorded every second. Draw the graph of the height of water level versus time for this container.


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    Basically I'm not sure how to draw the graph, I'm not sure what values to use etc. Can anyone help me out? I just need to know what values to use and why I have to use those values..

    Thanks
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  2. #2
    Super Member Bacterius's Avatar
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    It depends on the shape of the container. If the container has no special features (basic cylinder), then it is just a straight line OR more likely a parabola. You need to know the surface of the bottom of the cylinder, and know the quantity of water poured each second into the cylinder. Then it is a basic multiplication/squaring.

    If the container is some exotic shape, then the graph may take any possible shape.

    Do you have any more information ? Maybe it might be a good idea to show us the illustration, I'm pretty sure it contains the information you need And don't try to hide it, I know you have an illustration
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  3. #3
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    yes there is abit more info... I did'nt know if I needed to post it or not but here's the illustration.






    I'm not sure if you get the image or not.... if it doesn't work I"ll tyr something else.
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  4. #4
    Super Member Bacterius's Avatar
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    Upload your image on a server (google has lots of links !), then put the link the website provides you between the [IMG] and [/IMG] tags
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  5. #5
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    Is it okay if I do it like this... I put it as an attachment
    Attached Thumbnails Attached Thumbnails Basic Graphing help-assign_4.gif  
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  6. #6
    Super Member Bacterius's Avatar
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    That's fine. Where is the scale ? Can you measure the illustration for us and put some values on the illustration, such as the full height and the base length ?
    Is it a 2D shape ? Don't we consider the water is poured in a 3-dimensional object ?
    There is a lot of information missing, please give everything you know otherwise there might be infinitely many solutions
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  7. #7
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    That is actually all the information from this question... There is no measures on the illustartion and they give no other information. maybe this is why I'm so confused on how to do it.
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  8. #8
    Super Member Bacterius's Avatar
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    Strange ... without a scale we cannot know exactly how much water has been poured. Is it a paper illustration ? Is the illustration annoted "not to scale", or is it allowed to take some measures on the image to get the scales ?
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  9. #9
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    nope the illustration says nothing like that... it just shows the picture of what I posted above.. other than that theres absolutley no other information.
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  10. #10
    Super Member Bacterius's Avatar
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    Then I guess you are going to have to measure your values on the illustration.
    Here is the way to do it in the general way :

    You know that the formula to calculate the area of a trapezium is :

    A = \frac{h(a + b)}{2}, where h is the height of the trapezium, a is the bottom length and b is the top length.
    You know the bottom and top lengths by measuring them on the illustration. Try to isolate h :

    A = \frac{h(a + b)}{2}

    2A = h(a + b)

    h = \frac{2A}{a + b}

    Good. Your equation thus is y = \frac{2A}{a + b}.
    But there is something missing : A. That would be our water quantity, I guess. Is there some relationship between the water poured into the container and the area taken by the water ? I guess so ... Can you work the rest from now ?
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  11. #11
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    Thanks for the help... I actually think we don't have to do that for this problem because we haven't been taught how to do it... Hold on there's another example, I"m going to post that and maybe it will help out a bit.. It's the same type of question but a different problem.
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  12. #12
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    Quote Originally Posted by agent2421 View Post
    Thanks for the help... I actually think we don't have to do that for this problem because we haven't been taught how to do it... Hold on there's another example, I"m going to post that and maybe it will help out a bit.. It's the same type of question but a different problem.
    Here's the other question which gave us an answer already... Maybe this will help me for the problem I'm trying to do... It looks almost the same, so maybe someone might be able to figure it out... Where i say Attachment #, just look at the attachment listed below and it's in the same order.




    Water is being poured at a constant rate into a container as shown below. What would the graph of the Height of the Water level related to the time look like?


    (Attachment 1)






    Let us look at the rate of change at various water levels:
    (Attachment 2)

    A The rate of change of the water level is not constant and decreases as it approaches the red line.

    B After the level passes the first red line the container becomes more narrow resulting in the rate of change of the water level to increase until the second red line

    C As the level reaches and passes the second red line the rate of change remains constant for the rest of the fill up. This is a narrow section so the rate is faster than the other major sections.

    (attachment 3)
    Attached Thumbnails Attached Thumbnails Basic Graphing help-rate_change1.gif   Basic Graphing help-rate_change2.gif   Basic Graphing help-rate_change3.gif  
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  13. #13
    Super Member Bacterius's Avatar
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    Yep. Do you understand this problem and the answer ? The only thing you have to understand in this type of question is : how does the shape of the container (or more accurately the width of the container at one height) influence the rate of the fill and the shape of the graph ?
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  14. #14
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    I still dont understand how to do it for my problem. I'm not the greatest at math and really have trouble with some of this stuff... I still have no idea how to do this question:



    Water is being poured into a container as illustrated below at a constant rate. The height of the water level is then recorded every second. Draw the graph of the height of water level versus time for this container.
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  15. #15
    Super Member Bacterius's Avatar
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    I honestly think they don't want you to calculate anything. They just want you to think and investigate how the water height would evoluate.
    It should give something like a square root graph (try plotting y = \sqrt{x} on your computer). Because it is harder and harder for the water to gain in height because your container gets larger and larger.
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